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Alex Tsekenis

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Everything posted by Alex Tsekenis

  1. Google H-bridge, read the datasheets of the parts your mentioned and come up with a schematic that we can work on. Post it here
  2. Try these guys: Avnet Electronics Marketing (Australia) Pty. Ltd. (Distributor, Allegro Products) 9B, 9-11 South Street Rydalmere NSW 2116 Sydney, Australia Phone: +61 2 9585 5511 Fax: +61 2 9585 5519 Web: www.avnet.com Email: [email protected] They might be wholesalers only, but they might point you to some retail shop that takes their stock from them. If this fails, post back and I will look up a big list of online suppliers that was posted on Elektor magazine recently.
  3. Here is how to connect the components. The wires dont need to be black and red, just make sure the positive (usually red) connection of the buzzer ends up to the positive connection of the 9V battery. The metal contacts can be aluminum foil, steel plates, copper pipes, anything. You will not be able to solder the wires on aluminum with standard solder.
  4. The electronic components will be just two small DC motors and a two channel DC motor speed controller. The DC motors you probably have already, the speed controller you can buy online, just google for 'DC motor controller'. The difficult part will be to make the mechanical systems.
  5. Is that a lot or is it just me? Have you tried replacing U5? Sorry, for some reason the forum removed my post notification from this topic.
  6. I do not know the answer to this but it will probably be in this book: http://www.amazon.co.uk/Handbook-Batteries-David-Linden/dp/0071359788/ref=sr_1_2?ie=UTF8&s=books&qid=1268218232&sr=8-2
  7. Unipolar 15V should be sufficient assuming the totem pole drivers at the output of the isolators conduct good enough. Quantitative calculations will reveal that. The schematic of the system will need to show a reference of the supply to the isolators to the emitter of the igbts like it is shown in the black&white schematic for pins 5. You dont need an isolated supply for the low-side igbts.
  8. I think a hum based system will be more appropriate here. The surface is quite big, it will probably act as a proximity detector if you go with capacitance sensing.
  9. Nice spot. I like the way you have arranged for the components on the DTE board.
  10. Adding on Hero's post, they look like this: The second type is probably what you are looking for for your capacitance meter. You can buy them very cheaply at your local electronics shop.
  11. kylefrink You can use your original 25V transformers connected in series like this: for a supply of +/-35VDC as Hero pointed out.
  12. Is this a multilayer board audioguru? What is the purpose of those features that look like vias? This IC packaging technique reminded me of those old grey Tetris handheld games with a little bump between the buttons and screen. Their ASIC was packed in the same way.
  13. Please rewrite your question in a way that makes sense. In its current form the sentences are not logically linked together.
  14. Did you not need a 3.75 Ohms load for a 150V source?
  15. I dont think your biggest problem will be getting the heat away. I am worried about the thermal resistance between the actual wire and the outside of the resistor. Maybe that will be your limiting factor. Use power resistors in aluminium heatsink (they will give that figure in their datasheet) and then mount everything on a big heatsink with a fan. Try to avoid oil, it is very messy. Consider adding more resistors in parallel to distribute the heat better.
  16. He is right, Rgk does affect holding current. I found these documents: http://www.littelfuse.com/data/en/Application_Notes/AN1001.pdf http://www.teccor.com/data/en/Application_Notes/AN1008.pdf http://us.st.com/stonline/products/literature/an/3563.pdf Especially the last one on page 7 has a graph that you will find useful. I was not aware of this. I am not sure why this is so. Anyway, very useful.
  17. Last time, holding current is a fundamental and fixed as far as gate resistor is concerned characteristic of the SCR.
  18. So how does the quote from wikipedia relate to gate resistor Vs holding current? I think SCR is now synonymous to Thyristor, although they used to be slightly different things.
  19. You sound like a good dad. Your son seems to have the nack: Ok, maybe it is a good time to learn soldering then and implement some circuits on a matrix board. Before doing so you can try the circuit on a breadboard. In this way he will be introduced to 'prototyping'. There are abundant sources where you can find little circuits. Magazines might be a bit too complex, online you will find all levels and you can choose what is suitable. Websites such as this one have a projects section. You might also find books with beginners project in your bookshop. Be selective about the projects you do, ask you son too. They need to be well documented and do something at the end of the day. LEDs and speakers are popular. Also, try to blend in some simple 'applied theory' circuits like a capacitor being charged with a resistor, or a diode and an LED. Your son will develop and intuition about what components do which I cannot stress enough how important it is. Finally, take all measures possible to shield your son from mains voltage but I am sure you have done this already. Also use an isolation transformer and a residual current breaker if you haven't. Part of the protection is to explain why it is dangerous. In a couple years time you can talk about logic gates and other integrated circuits. Stay away from programmable devices such as microcontrollers at the moment as they are a 'black box' to the beginner. Dont worry too much about the course of learning you take. Although your son seems to be already autonomous with his hobby, some supervision is advisable. Soon your role will change from demonstrator to student therefore be prepared to recognise your son's achievements, as I am sure you would do anyway. Keep reminding him of safety though. Since you will be the one funding his hobby for the years to come, bite the bullet and choose high quality equipment with safety certificates. Even a simple screw driver can slip and injure your hand if the tip is made from a cheap soft alloy. If you have any questions please do ask here. Good luck and well done for your efforts.
  20. Post of picture of some sparks in the dark.
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